CNC Gear Shaping
A hob is the right choice until the gear you need has a shoulder sitting too close to the teeth. Then the hob has nowhere to run out, and the job stalls. Internal ring gears create the same problem, since there’s no clean way to run a hob around the inside of a bore. This is where CNC gear shaping justifies its floor space, reaching into geometry that other cutting methods can’t touch.
The generating action is the one you already know from any shaper, with the cutter reciprocating through the blank as the two roll together. What CNC adds is precise control over the stroke and infeed, as well as synchronized rotation of the cutter and blank. The tooth profile holds and repeats across a run without a setter chasing it. At JK Pulley & Manufacturing, we treat gear work as an engineering conversation before it ever becomes chips on the floor.
The reason a shop considers shaping usually comes down to clearance. Internal gears are the classic example, whether that’s a ring gear in a planetary set or another internal-tooth configuration. Cluster gears are another reason. When two gears sit stacked on one shaft with barely a gap between them, a shaper cutter can work the smaller gear right up against the larger one where a hob would crash. Shoulders and flanges fall into the same category. Blind pockets do, too. If a feature blocks tool runout, CNC gear shaping is often the answer.
Shaping and hobbing get talked about together, but there is a difference. A hob is a worm-shaped cutter that feeds continuously along the blank as the two rotate in mesh. That continuous action makes it fast on external spur and helical gears in quantity. Shaping trades that speed for reach. Working one tooth space at a time with a reciprocating stroke is slower, but it puts a cutter where a hob can’t go. For most external gears with room to run out, hobbing is the economical call. The moment the geometry closes in, shaping is what gets the part cut at all.
Shaping handles helical gears too, using a helical guide matched to the required helix angle. On shorter runs it can cut tooling costs, since one stock cutter covers a range of tooth counts at a given pitch and pressure angle. It also handles tooth modifications. When an application calls for crowning or tip relief, our team builds those into the machining process. Our gear cutting team weighs volume against geometry on every quote so the part gets made right the first time.
Industries using compact, high-load drivetrains lean on CNC gear shaping. Automotive and off-highway transmissions use internal ring gears throughout their planetary stages. Industrial gearboxes and speed reducers depend on them heavily. So do agricultural equipment and material handling systems. Aerospace and defense work demands tight-tolerance internal gearing, where inspection matters as much as the cut itself. Plenty of the gears started life as a worn OEM part with no drawing left, which is why reverse engineering runs alongside our gear work.
Quality on a shaped gear comes down to setup and inspection. Cutter sharpness shows up in the final tooth form along with stroke length and blank concentricity. We can hold tolerances as tight as 0.0005 inch where the application requires it, with inspection performed on a CMM as part of our quality process. JK Pulley & Manufacturing has been cutting gears at our plant in St. Louis since 1973, and our processes carry ISO 9001:2015 certification.
Material is rarely a constraint. We shape and cut gears in steel and alloy steel for high-stress drivetrains. Stainless steel can handle corrosive environments. Softer materials such as bronze or aluminum come into play when weight or wear behavior drives the design.
Getting CNC gear shaping right starts with your print and an honest look at how the gear has to run. Send us the drawing, or the worn part if the drawing’s long gone, and we’ll tell you whether shaping or hobbing is the right call. Call the JK Pulley & Manufacturing team in St. Louis at 314-481-2900 or request a quote and we’ll get to work on it.
